Osseointegrated dental implants are being used in prosthetic reconstruction for maxillofacial prosthetic patients (patients who have sustained the loss of oral or facial anatomy due to trauma, congenital anomaly or oncological disease) to aid in the retention of intraoral and facial prostheses. These implants combined with a mechanical attachment (i.e. magnets, clip-bar) embedded in the prosthesis provided a superior, more predictable result in retention of prostheses as compared to other retentive methods (i.e. adhesives). Many of these patients with oncological disease receive radiation therapy. Typically, patients who have received radiotherapy have not undergone implant treatment. This is due to a lack of research determining the predictability of osseointegration in irradiated bone. The purpose of this study is to provide needed preliminary information to asess the effects upon osseointegration when these implants are placed into previously irradiated bone. The specific aims of the project are to evaluate qualitatively and quantitatively and new bone formation around the implants and surrounding areas six months following implantation in irradiated bone in a suitable animal model. This implantation will be performed after a healing period of six months has elapsed following exposure of the bony site to a prescribed fractionated course of radiation therapy. In addition, qualitative and quantitative evaluations will be made for the presence of any other bone formation (i.e. necrotic bone), fibroplasia and vascular changes (i.e. thrombosis, angiogenesis). The significance of the study will be to provide prelimunary information regarding feasible and predictable outcomes for clinical use of this implant system in prosthetic reconstruction for humans who have undergone radiotherapy. Six young adult mongrel dogs will be used for this study. The dogs will be randomly divided into two equal groups. Each group will receive a different dose of radiation given in a fractionated regiment (30Gy and 60Gy respectively). The proposed protocol will involve radiotherapy to the zygomatic arch and occipital crest on one side of the dog's head. The opposing side will be protected from and radiation. This side will serve as a control. After a six month rest period following the completion of radiotherapy, implants will be placed into both the irradiated and control sides. After a six month healing period, the implants will be recovered for analysis following euthanasia of the animals. The results from this study will serve to direct future long-term investigations in this area.